AlGaAs/GaAsNSb heterojunction bipolar transistors (HBTs) with low turn-on voltage have been fabricated. The turn-on voltage of the device fabricated from an as-grown sample is ∼180 mV lower than that of a conventional AlGaAs/GaAs HBT. The effect of rapid thermal annealing on device performance is an increase in the gain from ∼8.5 to ∼20. However, the knee voltage of the annealed sample (∼3 V), as well as the turn-on voltage, is also higher compared with that of the as-grown sample (∼1.5 V).

Characteristics of an InGaP / Al X Ga 1 − X As / GaAs composite-emitter heterojunction bipolar transistor (CEHBT)A GaAsNSb heterojunction bipolar transistor ͑HBT͒ structure was grown by solid source molecular beam epitaxy. The fabricated HBT showed a reduction in the turn-on voltage of ϳ195 mV when GaAs 0.915 N 0.005 Sb 0.08 was used as the base material. The small knee voltage ͑Ͻ1 V͒ of the GaAsNSb HBT indicates that the current blocking effect is small. Significant gain degradation in the GaAsNSb HBT was observed when the nitrogen ͑N͒ composition was increased to 2%. The results show that the dilute nitride GaAsNSb materials have potential for reducing the turn-on voltage in GaAs HBTs.